From 06cf6f2ed0b19629700794727d86ed57b9c0583e Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Tue, 20 Jun 2006 12:56:49 -0400 Subject: [PATCH] NFS: Eliminate nfs_get_user_pages() Neil Brown observed that the kmalloc() in nfs_get_user_pages() is more likely to fail if the I/O is large enough to require the allocation of more than a single page to keep track of all the pinned pages in the user's buffer. Instead of tracking one large page array per dreq/iocb, track pages per nfs_read/write_data, just like the cached I/O path does. An array for pages is already allocated for us by nfs_readdata_alloc() (and the write and commit equivalents). This is also required for adding support for vectored I/O to the NFS direct I/O path. The original reason to pin the user buffer and allocate all the NFS data structures before trying to schedule I/O was to ensure all needed resources are allocated on the client before starting to send requests. This reduces the chance that resource exhaustion on the client will cause a short read or write. On the other hand, for an application making very large application I/O requests, this means that it will be nearly impossible for the application to make forward progress on a resource-limited client. Thus, moving the buffer pinning functionality into the I/O scheduling loops should be good for scalability. The next patch will do the same for NFS data structure allocation. Signed-off-by: Chuck Lever Signed-off-by: Trond Myklebust --- fs/nfs/direct.c | 205 ++++++++++++++++++++++------------------ include/linux/nfs_xdr.h | 2 + 2 files changed, 113 insertions(+), 94 deletions(-) diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 4cb3446220ba..b1630d53fbb1 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -73,8 +73,6 @@ struct nfs_direct_req { struct nfs_open_context *ctx; /* file open context info */ struct kiocb * iocb; /* controlling i/o request */ struct inode * inode; /* target file of i/o */ - struct page ** pages; /* pages in our buffer */ - unsigned int npages; /* count of pages */ /* completion state */ atomic_t io_count; /* i/os we're waiting for */ @@ -104,6 +102,20 @@ static inline int put_dreq(struct nfs_direct_req *dreq) return atomic_dec_and_test(&dreq->io_count); } +/* + * "size" is never larger than rsize or wsize. + */ +static inline int nfs_direct_count_pages(unsigned long user_addr, size_t size) +{ + int page_count; + + page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT; + page_count -= user_addr >> PAGE_SHIFT; + BUG_ON(page_count < 0); + + return page_count; +} + /** * nfs_direct_IO - NFS address space operation for direct I/O * @rw: direction (read or write) @@ -143,40 +155,6 @@ static void nfs_direct_release_pages(struct page **pages, int npages) page_cache_release(pages[i]); } -static inline int nfs_get_user_pages(int rw, unsigned long user_addr, size_t size, struct page ***pages) -{ - int result = -ENOMEM; - unsigned long page_count; - size_t array_size; - - page_count = (user_addr + size + PAGE_SIZE - 1) >> PAGE_SHIFT; - page_count -= user_addr >> PAGE_SHIFT; - - array_size = (page_count * sizeof(struct page *)); - *pages = kmalloc(array_size, GFP_KERNEL); - if (*pages) { - down_read(¤t->mm->mmap_sem); - result = get_user_pages(current, current->mm, user_addr, - page_count, (rw == READ), 0, - *pages, NULL); - up_read(¤t->mm->mmap_sem); - if (result != page_count) { - /* - * If we got fewer pages than expected from - * get_user_pages(), the user buffer runs off the - * end of a mapping; return EFAULT. - */ - if (result >= 0) { - nfs_direct_release_pages(*pages, result); - result = -EFAULT; - } else - kfree(*pages); - *pages = NULL; - } - } - return result; -} - static inline struct nfs_direct_req *nfs_direct_req_alloc(void) { struct nfs_direct_req *dreq; @@ -233,13 +211,8 @@ out: } /* - * We must hold a reference to all the pages in this direct read request - * until the RPCs complete. This could be long *after* we are woken up in - * nfs_direct_wait (for instance, if someone hits ^C on a slow server). - * - * In addition, synchronous I/O uses a stack-allocated iocb. Thus we - * can't trust the iocb is still valid here if this is a synchronous - * request. If the waiter is woken prematurely, the iocb is long gone. + * Synchronous I/O uses a stack-allocated iocb. Thus we can't trust + * the iocb is still valid here if this is a synchronous request. */ static void nfs_direct_complete(struct nfs_direct_req *dreq) { @@ -297,6 +270,11 @@ static struct nfs_direct_req *nfs_direct_read_alloc(size_t nbytes, size_t rsize) return dreq; } +/* + * We must hold a reference to all the pages in this direct read request + * until the RPCs complete. This could be long *after* we are woken up in + * nfs_direct_wait (for instance, if someone hits ^C on a slow server). + */ static void nfs_direct_read_result(struct rpc_task *task, void *calldata) { struct nfs_read_data *data = calldata; @@ -305,6 +283,9 @@ static void nfs_direct_read_result(struct rpc_task *task, void *calldata) if (nfs_readpage_result(task, data) != 0) return; + nfs_direct_dirty_pages(data->pagevec, data->npages); + nfs_direct_release_pages(data->pagevec, data->npages); + spin_lock(&dreq->lock); if (likely(task->tk_status >= 0)) @@ -314,11 +295,8 @@ static void nfs_direct_read_result(struct rpc_task *task, void *calldata) spin_unlock(&dreq->lock); - if (put_dreq(dreq)) { - nfs_direct_dirty_pages(dreq->pages, dreq->npages); - nfs_direct_release_pages(dreq->pages, dreq->npages); + if (put_dreq(dreq)) nfs_direct_complete(dreq); - } } static const struct rpc_call_ops nfs_read_direct_ops = { @@ -328,21 +306,23 @@ static const struct rpc_call_ops nfs_read_direct_ops = { /* * For each nfs_read_data struct that was allocated on the list, dispatch - * an NFS READ operation + * an NFS READ operation. If get_user_pages() fails, we stop sending reads. + * Read length accounting is handled by nfs_direct_read_result(). + * Otherwise, if no requests have been sent, just return an error. */ -static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos) +static ssize_t nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos) { struct nfs_open_context *ctx = dreq->ctx; struct inode *inode = ctx->dentry->d_inode; struct list_head *list = &dreq->list; - struct page **pages = dreq->pages; size_t rsize = NFS_SERVER(inode)->rsize; - unsigned int curpage, pgbase; + unsigned int pgbase; + int result; + ssize_t started = 0; + struct nfs_read_data *data; - curpage = 0; pgbase = user_addr & ~PAGE_MASK; do { - struct nfs_read_data *data; size_t bytes; bytes = rsize; @@ -353,13 +333,21 @@ static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long data = list_entry(list->next, struct nfs_read_data, pages); list_del_init(&data->pages); + data->npages = nfs_direct_count_pages(user_addr, bytes); + down_read(¤t->mm->mmap_sem); + result = get_user_pages(current, current->mm, user_addr, + data->npages, 1, 0, data->pagevec, NULL); + up_read(¤t->mm->mmap_sem); + if (unlikely(result < data->npages)) + goto out_err; + data->inode = inode; data->cred = ctx->cred; data->args.fh = NFS_FH(inode); data->args.context = ctx; data->args.offset = pos; data->args.pgbase = pgbase; - data->args.pages = &pages[curpage]; + data->args.pages = data->pagevec; data->args.count = bytes; data->res.fattr = &data->fattr; data->res.eof = 0; @@ -382,17 +370,36 @@ static void nfs_direct_read_schedule(struct nfs_direct_req *dreq, unsigned long bytes, (unsigned long long)data->args.offset); + started += bytes; + user_addr += bytes; pos += bytes; pgbase += bytes; - curpage += pgbase >> PAGE_SHIFT; pgbase &= ~PAGE_MASK; count -= bytes; } while (count != 0); BUG_ON(!list_empty(list)); + return 0; + +out_err: + if (result > 0) + nfs_direct_release_pages(data->pagevec, result); + + list_add(&data->pages, list); + while (!list_empty(list)) { + data = list_entry(list->next, struct nfs_read_data, pages); + list_del(&data->pages); + nfs_readdata_free(data); + if (put_dreq(dreq)) + nfs_direct_complete(dreq); + } + + if (started) + return 0; + return result < 0 ? (ssize_t) result : -EFAULT; } -static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, unsigned int nr_pages) +static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos) { ssize_t result; sigset_t oldset; @@ -404,8 +411,6 @@ static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size if (!dreq) return -ENOMEM; - dreq->pages = pages; - dreq->npages = nr_pages; dreq->inode = inode; dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data); if (!is_sync_kiocb(iocb)) @@ -413,8 +418,9 @@ static ssize_t nfs_direct_read(struct kiocb *iocb, unsigned long user_addr, size nfs_add_stats(inode, NFSIOS_DIRECTREADBYTES, count); rpc_clnt_sigmask(clnt, &oldset); - nfs_direct_read_schedule(dreq, user_addr, count, pos); - result = nfs_direct_wait(dreq); + result = nfs_direct_read_schedule(dreq, user_addr, count, pos); + if (!result) + result = nfs_direct_wait(dreq); rpc_clnt_sigunmask(clnt, &oldset); return result; @@ -426,9 +432,9 @@ static void nfs_direct_free_writedata(struct nfs_direct_req *dreq) while (!list_empty(&dreq->list)) { struct nfs_write_data *data = list_entry(dreq->list.next, struct nfs_write_data, pages); list_del(&data->pages); + nfs_direct_release_pages(data->pagevec, data->npages); nfs_writedata_release(data); } - nfs_direct_release_pages(dreq->pages, dreq->npages); } #if defined(CONFIG_NFS_V3) || defined(CONFIG_NFS_V4) @@ -672,21 +678,23 @@ static const struct rpc_call_ops nfs_write_direct_ops = { /* * For each nfs_write_data struct that was allocated on the list, dispatch - * an NFS WRITE operation + * an NFS WRITE operation. If get_user_pages() fails, we stop sending writes. + * Write length accounting is handled by nfs_direct_write_result(). + * Otherwise, if no requests have been sent, just return an error. */ -static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync) +static ssize_t nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long user_addr, size_t count, loff_t pos, int sync) { struct nfs_open_context *ctx = dreq->ctx; struct inode *inode = ctx->dentry->d_inode; struct list_head *list = &dreq->list; - struct page **pages = dreq->pages; size_t wsize = NFS_SERVER(inode)->wsize; - unsigned int curpage, pgbase; + unsigned int pgbase; + int result; + ssize_t started = 0; + struct nfs_write_data *data; - curpage = 0; pgbase = user_addr & ~PAGE_MASK; do { - struct nfs_write_data *data; size_t bytes; bytes = wsize; @@ -695,6 +703,15 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long BUG_ON(list_empty(list)); data = list_entry(list->next, struct nfs_write_data, pages); + + data->npages = nfs_direct_count_pages(user_addr, bytes); + down_read(¤t->mm->mmap_sem); + result = get_user_pages(current, current->mm, user_addr, + data->npages, 0, 0, data->pagevec, NULL); + up_read(¤t->mm->mmap_sem); + if (unlikely(result < data->npages)) + goto out_err; + list_move_tail(&data->pages, &dreq->rewrite_list); data->inode = inode; @@ -703,7 +720,7 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long data->args.context = ctx; data->args.offset = pos; data->args.pgbase = pgbase; - data->args.pages = &pages[curpage]; + data->args.pages = data->pagevec; data->args.count = bytes; data->res.fattr = &data->fattr; data->res.count = bytes; @@ -727,17 +744,36 @@ static void nfs_direct_write_schedule(struct nfs_direct_req *dreq, unsigned long bytes, (unsigned long long)data->args.offset); + started += bytes; + user_addr += bytes; pos += bytes; pgbase += bytes; - curpage += pgbase >> PAGE_SHIFT; pgbase &= ~PAGE_MASK; count -= bytes; } while (count != 0); BUG_ON(!list_empty(list)); + return 0; + +out_err: + if (result > 0) + nfs_direct_release_pages(data->pagevec, result); + + list_add(&data->pages, list); + while (!list_empty(list)) { + data = list_entry(list->next, struct nfs_write_data, pages); + list_del(&data->pages); + nfs_writedata_free(data); + if (put_dreq(dreq)) + nfs_direct_write_complete(dreq, inode); + } + + if (started) + return 0; + return result < 0 ? (ssize_t) result : -EFAULT; } -static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos, struct page **pages, int nr_pages) +static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, size_t count, loff_t pos) { ssize_t result; sigset_t oldset; @@ -753,8 +789,6 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz if (dreq->commit_data == NULL || count < wsize) sync = FLUSH_STABLE; - dreq->pages = pages; - dreq->npages = nr_pages; dreq->inode = inode; dreq->ctx = get_nfs_open_context((struct nfs_open_context *)iocb->ki_filp->private_data); if (!is_sync_kiocb(iocb)) @@ -765,8 +799,9 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz nfs_begin_data_update(inode); rpc_clnt_sigmask(clnt, &oldset); - nfs_direct_write_schedule(dreq, user_addr, count, pos, sync); - result = nfs_direct_wait(dreq); + result = nfs_direct_write_schedule(dreq, user_addr, count, pos, sync); + if (!result) + result = nfs_direct_wait(dreq); rpc_clnt_sigunmask(clnt, &oldset); return result; @@ -796,8 +831,6 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, loff_t pos) { ssize_t retval = -EINVAL; - int page_count; - struct page **pages; struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; @@ -819,14 +852,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, char __user *buf, size_t count, if (retval) goto out; - retval = nfs_get_user_pages(READ, (unsigned long) buf, - count, &pages); - if (retval < 0) - goto out; - page_count = retval; - - retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos, - pages, page_count); + retval = nfs_direct_read(iocb, (unsigned long) buf, count, pos); if (retval > 0) iocb->ki_pos = pos + retval; @@ -862,8 +888,6 @@ out: ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t pos) { ssize_t retval; - int page_count; - struct page **pages; struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; @@ -891,14 +915,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, const char __user *buf, size_t if (retval) goto out; - retval = nfs_get_user_pages(WRITE, (unsigned long) buf, - count, &pages); - if (retval < 0) - goto out; - page_count = retval; - - retval = nfs_direct_write(iocb, (unsigned long) buf, count, - pos, pages, page_count); + retval = nfs_direct_write(iocb, (unsigned long) buf, count, pos); /* * XXX: nfs_end_data_update() already ensures this file's diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h index 7c7320fa51aa..2d3fb6416d91 100644 --- a/include/linux/nfs_xdr.h +++ b/include/linux/nfs_xdr.h @@ -729,6 +729,7 @@ struct nfs_read_data { struct list_head pages; /* Coalesced read requests */ struct nfs_page *req; /* multi ops per nfs_page */ struct page **pagevec; + unsigned int npages; /* active pages in pagevec */ struct nfs_readargs args; struct nfs_readres res; #ifdef CONFIG_NFS_V4 @@ -747,6 +748,7 @@ struct nfs_write_data { struct list_head pages; /* Coalesced requests we wish to flush */ struct nfs_page *req; /* multi ops per nfs_page */ struct page **pagevec; + unsigned int npages; /* active pages in pagevec */ struct nfs_writeargs args; /* argument struct */ struct nfs_writeres res; /* result struct */ #ifdef CONFIG_NFS_V4 -- 2.20.1